Cataracts are the leading cause of blindness worldwide, accounting for 42 percent of all blindness. The long-term goal of this application is to provide an understanding of the role of oxidation in the etiology of human age-onset cataracts. Transgenic animal models and gene knockouts for specific antioxidant enzymes serve as powerful tools to assess the role of these enzymes in cataract formation. We have recently found that gene knockout of glutathione peroxidase-l (GPX-l) leads to increased nuclear light scattering (NLS) compared to age-matched controls. The increased NLS appears to be related to lens fiber membrane damage as seen by transmission and confocal microscopy. The hypothesis that deficiency of GPX-l leads to membrane protein modification and lipid peroxidation in nuclear fibers will be tested by Scheimpflug slit lamp and dynamic light scattering measurements. Attempts will be made to study changes in lens transparency in other transgenic animal models, which lack the enzyme CuZn superoxide dismutase (CuZnSOD). Additional specific aims are to up and down regulate Mn superoxide dismutase and CuZnSOD in the recently established human lens epithelial cell line (SRA 01/04) by transfection with plasmids containing sense and antisense cDNA for these enzymes. We will then subject the cells to various oxidative challenges including H202, X-ray, UV radiation and hyperbaric oxygen to study their effect on cation transport and cell membranes. The efficiency of transfection will be determined by enzyme assays, Western and Northern blot analyses. The ability of these cell lines to resist the cytotoxic effects of oxidative stress will be assessed from changes in cell proliferation, cell morphology, DNA strand breaks, immunocytochemistry, protein modification and lipid peroxide formation.